The thing that I like about this piece are his eyes. They're focused on something and I think at the position he's at, it's sort of complicated. It worked though, well. I like the value you did around his hairline. Something seems off around the mouth,though. I think if you tried pen and ink it might show you the difference between line and value. Faces are full of values. You have great structure, but having plain lines make it look more like a sketch.